A novel promoter architecture for microaerobic activation by the anaerobic transcription factor FNR

The yfiD gene of Escherichia coli has an unusual promoter architecture in which an FNR dimer located at −93.5 inhibits transcription activation mediated by another FNR dimer bound at the typical class II position (−40.5). In vitro transcription from the yfiD promoter indicated that FNR alone can dow...

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Published in:Molecular microbiology Vol. 39; no. 3; pp. 747 - 753
Main Authors: Marshall, Fiona A., Messenger, Sarah L., Wyborn, Neil R., Guest, John R., Wing, Helen, Busby, Stephen J. W., Green, Jeffrey
Format: Journal Article
Language:English
Published: Oxford, UK Blackwell Science, Ltd 01-02-2001
Blackwell Publishing Ltd
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Summary:The yfiD gene of Escherichia coli has an unusual promoter architecture in which an FNR dimer located at −93.5 inhibits transcription activation mediated by another FNR dimer bound at the typical class II position (−40.5). In vitro transcription from the yfiD promoter indicated that FNR alone can downregulate yfiD expression. Analysis of yfiD::lac reporters showed that five turns of the DNA helix between FNR sites was optimal for downregulation. FNR heterodimers, in which one subunit carried a defective repression surface, revealed that the upstream subunit of the −40.5 dimer and the downstream subunit of the −93.5 dimer were most important for downregulating yfiD expression. Deletion of the C‐terminal domain of the α‐subunit of RNA polymerase (RNAP) did not affect FNR‐mediated repression, suggesting that repression is mediated through FNR–FNR and not FNR–RNAP interactions. Maximum yfiD::lac expression was observed in cultures exposed to 10 µM oxygen. More or less oxygen reduced expression dramatically. This pattern of response was dependent on the combination of a high‐affinity site at the activating class II position and a lower affinity site at the upstream position.
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ISSN:0950-382X
1365-2958
DOI:10.1046/j.1365-2958.2001.02262.x